A high-fat diet and long-term exposure to air pollution are both associated with worse outcomes in patients with ankylosing spondylitis, a study shows.
The study, “Effect of food intake and ambient air pollution exposure on ankylosing spondylitis disease activity,” was published in the journal Advances in Rheumatology.
Ankylosing spondylitis is an immune-mediated rheumatic disease characterized by chronic and progressive inflammation involving the back, neck, and the lower spine and hip joints. This condition is associated with physical impairments caused by decreased spinal mobility and severe pain that can affect daily life.
The activity of ankylosing spondylitis significantly varies between patients: While some have only minimal symptoms, others may experience aggressive and widespread manifestations. Although it is not yet fully understood why this happens, it is believed that genetic and environmental factors may have a critical role.
Increasing evidence has shown that diet and air pollution can contribute toward the inflammatory process in human health and disease. Now Tehran University of Medical Sciences researchers have explored the role of these two environmental factors in disease activity and functional impairment in ankylosing spondylitis.
The team recruited 30 patients with ankylosing spondylitis from the Iranian Ankylosing Spondylitis Association and 30 age- and sex-matched healthy volunteers used as controls.
Approximately 43% of patients and 30% of the controls were active smokers. However, no significant difference was found in disease activity, as measured by three different scales — BASMI, BASFI, and BASDAI — between patients who were smokers and those who were nonsmokers.
When looking specifically at diet, ankylosing spondylitis patients had about a 1.2 times higher mean caloric consumption and fat intake than controls. Total fat intake had a weak correlation with the BASFI score of disease activity in the patient group.
In particular, patients were found to eat foods that were richer in saturated fat, monounsaturated fatty acids, and polyunsaturated fatty acids (three types of fatty molecules). Consumption of all three of these fats was moderately correlated with BASFI scores, and monounsaturated fatty acid intake was also moderately correlated with BASMI scores in ankylosing spondylitis patients.
“Among all the essential components that were measured like proteins, the amount of carbohydrates, energy intake and fat intake in the patient group was significantly higher than the control group,” the researchers wrote.
Many fatty molecules can trigger cellular signals and modulate the response of immune cells. As a result, they can play an active role in the proinflammatory status of these patients, which can further explain the relationship among diet, fat intake, and disease activity.
In general, patients also consumed higher amounts of several vitamins (A, B1, B2, C) and minerals (potassium, calcium, iron, phosphorus, magnesium, zinc, copper, and selenium) than the healthy volunteers. Still, only higher vitamin E intake was found to be moderately associated with higher BASMI scores in the patient group.
Air pollution exposure was not different between patients and controls. However, patients who had been exposed to a specific type of pollutant particles (atmospheric particulate matter with a diameter of less than 2.5 micrometers) over the long term had higher BASFI, BASDI, and BASMI scores, suggesting a strong correlation between air pollution and ankylosing spondylitis disease activity.
These findings “reveal a new perspective to air pollution effects on ankylosing spondylitis,” according to the researchers.
Additional studies are still needed to further explore the possibility of using dietary programs as a management strategy for this population. In addition, the team believes that “living in areas with lower air pollution might be a solution for ankylosing spondylitis patients” to control their disease.